http://www.geocities.com/hollywood/hills/1742/specials.html
That guy has both SPFX and Making of Empire Strikes Back available for trade. I'm thinking that perhaps this may not be as rare as we think, which is good because maybe we can see it.
Additionally, check out:
http://www.lucasfan.com/swtv/tapes.doc
I remember trading with this guy years ago, and he was great to deal with. My point is that while he doesn't have the Making of Empire special, he does have a ton of stuff related to Empire that I haven't seen anywhere else. I have to go through my old Star Wars VHS compilations (of which I have 8 or so) to see what of this stuff I have to share with all of you. (And especially those of you who can turn VHS to AVI or DVD).